Assessing the Size Effect on Microwave Fracturing of Diorite Using a Dielectric-Loaded Converging Waveguide Antenna

Microwave fracturing and assisted mechanical breakage of rocks has been demonstrated to be efficient and cost-effective, holding great potential in rock excavation. However, the size effect on the fracturing process using open-ended microwave antennas has not been well studied or understood. To address this issue, a dielectric-loaded converging antenna is used to heat and fracture diorite specimens of different dimensions. The study investigates the effect of specimen plane size and thickness, as well as microwave energy, on the crack characteristics. The results show that as specimen plane size increases, fracturing becomes more localized with shorter and narrower cracks. Conversely, specimen thickness is negatively correlated with crack characteristics on the microwave-treated surface. The study also defines and examines the representative elementary volume (REV) of microwave fracturing using the antenna. Regression models are developed and validated to predict crack characteristics such as number, density, total length, and maximum width. The paper concludes by discussing the arrangement of microwave radiations on rock masses with different joint spacings using the antenna.